US4531602A - Power steering system - Google Patents

Power steering system Download PDF

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Publication number
US4531602A
US4531602A US06/510,196 US51019683A US4531602A US 4531602 A US4531602 A US 4531602A US 51019683 A US51019683 A US 51019683A US 4531602 A US4531602 A US 4531602A
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US
United States
Prior art keywords
pressure
valve
steering system
modulating valve
connection
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Fee Related
Application number
US06/510,196
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English (en)
Inventor
Arno Roehringer
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Daimler Benz AG
Original Assignee
Daimler Benz AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from DE19823225053 external-priority patent/DE3225053C2/de
Priority claimed from DE19823247745 external-priority patent/DE3247745C2/de
Application filed by Daimler Benz AG filed Critical Daimler Benz AG
Assigned to DAIMLER-BENZ AKTIENGESELLSCHAFT STUTTGART, GERMANY reassignment DAIMLER-BENZ AKTIENGESELLSCHAFT STUTTGART, GERMANY ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: ROEHRINGER, ARNO
Application granted granted Critical
Publication of US4531602A publication Critical patent/US4531602A/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62D—MOTOR VEHICLES; TRAILERS
    • B62D6/00—Arrangements for automatically controlling steering depending on driving conditions sensed and responded to, e.g. control circuits

Definitions

  • the invention concerns a power steering system of the type which includes a steering servo-motor with a steering assist piston acted on by fluid pressure in respective oppositely facing working chambers and a servo-valve for controlling fluid pressure supply to the working chambers in dependance on the position of a servo-valve adjusting member which is operatively connected to the vehicle hand steering wheel.
  • Reaction pressure chambers at opposite sides of the servo-valve adjusting member are connected by pressure connections to the working chambers to communicate steering feedback to the driver.
  • This type of system includes modulating valve means for modulating the reaction pressure which is communicated back to the steering servo-motor, typically as a function of engine speed.
  • An object of the invention is to so arrange a power steering system of this type that the modulating valve can be in a shut-off position, in which flow through it is prevented, when the travelling speed tends toward zero.
  • a modulating valve is arranged in a short-circuit bypass connection between the two reaction chambers and the pressure connections between the reaction chambers and working chambers are continuously open.
  • the two reaction pressure chambers of the control valve are short-circuited via the throttle even when the modulating valve is in the shut-off position, so that, on the one hand, quantities of leakage oil are avoided and, on the other hand, the function of the control valve is not adversely affected.
  • the modulating valve is inserted between the reaction pressure chamber and the valve connection, associated with the operating pressure chamber, of the control valve, so that two pressure connections are necessary between the modulating valve and the control valve and the unreduced operating pressure of the power steering system arises as the output pressure at the modulating valve during a corresponding steering activity.
  • the constructional and spatial requirement for the control valve is also large because the reaction pressure chamber has to be arranged fully independent of the valve connections of the control valve.
  • a modulating valve operating as a function of the travelling speed and/or other parameters is, indeed, used to produce a reaction pressure dependent on the parameters but the feedback which can be felt at the hand steering wheel results from a differential pressure brought into effect at the valve setting element by means of additional reaction pressure pistons.
  • This differential pressure is produced from the full operating pressure and the reaction pressure set by the modulating valve, so that the differential pressure which can be felt as the feedback can assume pressure values between zero and the actual value of the operating pressure.
  • the modulating valve is arranged to shut off the pressure connection at low traveling speeds.
  • the respective pressure connections which bypass the modulating valve and connect the reaction and operating pressure chambers are provided with a constant throttle and the modulating valve is configured to produce a pressure drop in the reaction pressure chamber at least indirectly relative to a pressure medium return which is substantially relieved of pressure.
  • reaction pressure chambers are located so as to be fixed in position relative to the valve housing of the servo-control valve.
  • Preferred embodiments further include a bypass throttle connection containing a throttle and connection parallel with the modulating valve.
  • a valve for limiting the pressure-dependent feedback connected in parallel with the modulating valve is provided.
  • a controllable shut-off valve arrangement is connected in parallel with the throttles disposed in the lines connecting the respective reaction and working chambers, which shut-off valve arrangement is located between the modulating valve and the pressure medium return.
  • reaction pressure chamber is connected to the respective operating pressure chamber via the associated valve connection of the servo-control valve.
  • the characteristics of the feedback can be modified by a bypass throttle connection, containing a throttle, to the modulating valve;
  • the feedback can be limited by a valve connected in parallel with the modulating valve
  • the characteristics of the feedback can be modulated by a controllable shut-off valve arrangement, which is connected in parallel with the throttle located between the modulating valve and the pressure medium return;
  • reaction pressure chamber is connected to the operating pressure chamber via the associated valve connection of the control valve
  • reaction pressure chamber is connected to the associated valve connection of the control valve by means of a pressure duct, which contains the throttle, of the valve setting element;
  • the throttle located between the modulating valve and the pressure medium return, is arranged downstream of the valve, for limiting the feedback
  • the modulating valve is inserted in series with at least one throttle between the operating pressure source, on one side, and a pressure medium return, substantially relieved of pressure, during a steering deflection of the manual steering wheel, the two reaction pressure chambers, each connected on one side to an operating pressure chamber, being connected to one another on the other side by means of a short-circuit pressure connection.
  • the short-circuit pressure connection contains the throttle located in series with the modulating valve and the modulating valve is inserted in the pressure connection between one reaction pressure chamber and the associated operating pressure chamber. In this manner, the modulating valve can be closed at low travelling speeds without the control valve being blocked in the process.
  • FIG. 1 is a hydraulic block circuit diagram of a power steering system constructed according to a first preferred embodiment of the invention
  • FIG. 2 is a hydraulic block circuit diagram of a power steering system constructed according to a second preferred embodiment of the invention.
  • FIG. 3 is a hydraulic block circuit diagram of a power steering system constructed according to a third preferred embodiment of the invention.
  • a steering spindle 37 has positive rotational connection, in a manner not shown, in each case with a hand steering wheel at one of its ends and a steering worm 4 (worm 4 schematically represented twice in the Figures) at the other end.
  • the steering worm 4 is, in turn supported in an operating cylinder 34 of a steering servo-motor 6 so that it can be rotated but not displaced axially and is connected with a steering nut 35 so that it can execute a screwing movement.
  • the steering nut 35 is supported so that it can rotate but cannot be displaced axially in an operating piston 33, which subdivides the operating cylinder 34 into two operating pressure chambers 13 and 14, which operating piston 33 is in drive connection in conventional manner with the drop arm of the vehicle steering system.
  • the steering nut 35 is equipped on its outer periphery with a radial control protrusion 36 rigidly connected to it, which radial control protrusion operates a valve setting element 8, embodied as an axial slide, of a control valve 5.
  • Two valve connections 15 and 16 of the control valve 5 are each connected via a pressure connection 38 or 39, respectively, to an associated operating pressure chamber 13 or 14, respectively.
  • Two other valve connections 40 and 41 of the control valve 5 are connected to a return flow line 22 used as pressure medium return, which return flow line leads to a pressure medium reservoir 42.
  • a pressure pump 17 extracting from the reservoir 42 is connected via its supply pressure line 43 to a further valve connection 44 of the control valve 5.
  • the valve setting element 8 is equipped with two control land pairs 45 and 46, by means of which it is possible to set at the operating piston 33 either pressure equilibrium for straight line travel or a differential pressure force, which supports the current steering deflection, by throttling or shutting off corresponding valve passages between the valve connections 15 and 16 on the one side and the valve connections 40, 41 and 44 on the other side.
  • the end surfaces of the valve setting element 8 are used as the corresponding reaction pressure surfaces 11 and 12, which are located in correspondingly formed reaction pressure chambers 9 and 10, respectively, which are rigidly positioned with respect to the valve housing 23 of the control valve 5.
  • control land pairs 45 and 46 are maintained in their neutral position (shown)--in which both valve connections 15 and 16 are connected to both the supply pressure line 43 and the return line 22--by a centering spring 47, which is supported between stop washers 48 and 49.
  • the stop washers 48 and 49 operate in conjunction with end stops 50 and 52 on the valve setting element 8 on the one side and with end stops 51 and 53 on the valve housing 23 on the other.
  • the valve setting element 8 is so deflected out of its neutral position by the control protrusion 36 after the preloading force of the centering spring 47 has been overcome, that a higher pressure occurs at the valve connection 15, and hence in the operating pressure chamber 13, than at the valve connection 16 and in the operating pressure chamber 14. So that a feedback can be felt at the hand steering wheel, the reaction pressure surface 11, which is effective in the opposite direction to the arrow direction 3, is subjected to a reaction pressure.
  • the associated reaction pressure chamber 9 is in connection with the effective operating pressure chamber 13 via a pressure connection 20 containing a throttle 18. In alternate preferred embodiments this connection can also be produced while bypassing the control valve 5 according to the dotted pressure connection 20a with throttle 18a.
  • the reaction pressure chamber 9 is also connected to a valve connection 54 of a modulating valve 7, with which a further valve connection 55 is, during the deflection of the valve setting element 8 mentioned, connected to the return line 22 in a manner which is further described below.
  • the modulating valve 7 produces a pressure drop between the reaction pressure chamber 9 and its valve connection 55 as a function of the travelling speed.
  • valve connection can also be connected directly to the return line 22.
  • a common modulating valve 7 is used for both reaction pressure chambers 9 and 10, because the reaction pressure chamber 10 not associated with the steering deflection 3 is connected by a pressure connection 21 (otherwise similar in function to the pressure connection 20 and containing a valve 19)--which can also be disposed in an alternate arrangement corresponding to the pressure connection 21a, shown dotted, with throttle 19a, thus bypassing the control valve 5--to the operating pressure which, in turn, is in at least throttle connection with the return line 22 via the control land pair 46.
  • the throttle 19, which with the operating pressure chamber 14 is effectively connected--i.e. with steering deflection in opposition to the arrow direction 3--is used for the proportional derivation of the output pressure in the reaction pressure chamber 10 from the operating pressure, is inserted between the connection 55 of the modulating valve 7 and the return line 22.
  • the common modulating valve 7 is inserted together with its valve connections 54 and 55 in a short-circuit pressure connection 32, which connects the reaction pressure chambers 9 and 10 to one another, so that with alternative steering deflection at the valve connections 54 and 55, alternating reaction pressure or return pressure occurs.
  • FIGS. 1 and 2 both embodiment forms of FIGS. 1 and 2 are similar in providing that the modulating valve 7 is connected in parallel with a bypass throttle connection 25 containing a throttle 24.
  • the two embodiment forms differ initially in the measures employed for limiting the manual force by their use of pressure limiting valves for the reaction pressure.
  • the two reaction pressure chambers 9 and 10 are connected to one another by means of a bypass short-circuit connection 56 bypassing the modulating valve 7 and the throttle 24 and two pressure limiting valves 26 and 27 operating in opposition are inserted in the short-circuit connection 56.
  • the throttle 19 or 18 of the currently ineffective reaction pressure chamber 10 or 9, respectively is still located between the currently operating pressure limiting valve 26 or 27, respectively, and the return line 22.
  • the pressure limiting valves 26 and 27 in the embodiment form of FIG. 2 are connected directly to the return line 22.
  • FIG. 2 shows a shut-off valve arrangement 28 or 29 parallel to the throttle 19 or 18, respectively, of the reaction pressure chamber 10 or 9, respectively, each arranged downstream of the return, this arrangement being also usable in the embodiment form of FIG. 1 according to other contemplated embodiments.
  • Each shut-off valve arrangement 28 or 29 closes initially under the influence of the operating pressure of the connected valve connection 15 or 16, respectively, for the associated steering deflection.
  • the shut-off valve arrangement connected with each of the reaction pressure chambers 9 or 10 inserted after the return line 22 is, however, controllable, in a manner not shown, so that the characteristic of the throttle 18 or 19 connected in parallel downstream of the return is variable.
  • the operating pressure chambers 13 and 14 of the steering system servo-motor 6 are each connected via a pressure connection 38 or 39 to the associated valve connection 15 or 16, respectively, of the control valve 5, which responds to angular deflections of a manual steering wheel (steering worm 4) and is connected via a supply pressure line 43 containing a pressure pump 17 and via a return line 22, which is substantially relieved of pressure, to a pressure medium reservoir 42.
  • the control valve has a so-called "open center 61" in its neutral position 58, i.e. all four connected lines 22, 38, 39 and 43 are connected to one another, so that pressure equilibrium exists at the operating piston 33, on the one hand, and also, on the other hand, at the reaction pressure surfaces 11 and 12 in the reaction pressure chambers 9 and 10 of the control valve 5--which chambers are each connected by means of a pressure connection 20 or 21, respectively, to one of the operating pressure chambers 13 or 14, respectively.
  • reaction pressure chambers 9 and 10 are connected to one another by means of a short-circuit pressure connection 32 containing a throttle 57.
  • a modulating valve 7 operating as a function of at least one parameter, in particular the travelling speed, sets the flow rate of the throttle 57 and is, for this purpose, inserted in one of the pressure connections 20 and 21, in the pressure connection 20 in the example shown.
  • the operating pressure chamber 13 On deflection of the control valve 5 into the position 59, the operating pressure chamber 13 is subjected to a higher pressure than the operating pressure chamber 14 and a pressure difference proportional to this is produced at the throttle 57, the magnitude of which can be influenced by the modulating valve 7. Because of the pressure difference at the throttle 57, a reaction pressure is built up in the reaction pressure chamber 9, which reaction pressure produces a reaction pressure force on the reaction pressure surface 11, which can be felt at the manual steering wheel.
  • the modulating valve 7 operates as a function of the travelling speed, it is intrinsically desirable that the reaction should be greater at higher travelling speeds than at lower travelling speeds. It is a corollary to this that the flow through the modulating valve 7--i.e. in the pressure connection 20--would be substantially unlimited as the travelling speed tends towards zero, i.e. also during parking with a high requirement for steering assistance, so that under these circumstances the modulating valve 7 would represent an undesirable leakage point, via which the pressure pump 17 would supply substantial leakage quantities back into the reservoir 42 while bypassing the steering system servo-motor 6.
  • the modulating valve 7 in quasi-parallel connection with the associated valve connection 15 of the control valve 5 is connected to the operating pressure chamber 13 and the throttle 57 is inserted in the short-circuit pressure connection 32, the modulating valve 7 can, without difficulty, be brought into a shut-off position closing the pressure connection 20 and thus preventing leakages, without this being able to cause blocking of the control valve 5.
  • a volume balance can result between the reaction pressure chambers 9 and 10 via the throttle 57. This effect also occurs if the control valve 5 is deflected in the opposite direction into its position 60, in which the other operating pressure chamber 14 is subjected to the higher pressure.
  • the throttle 57 is not behind but in front of the modulating valve 7 in the flow path--but nothing changes with respect to the possibility quoted for volume balance or with respect to the function of the modulating valve 7 in determining the pressure difference at the throttle 57.
  • the modulating valve 7--as is indicated dotted at 7a--is located in the pressure connection 21 of the other reaction pressure chamber 10.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Transportation (AREA)
  • Mechanical Engineering (AREA)
  • Steering Control In Accordance With Driving Conditions (AREA)
  • Power Steering Mechanism (AREA)
US06/510,196 1982-07-05 1983-07-01 Power steering system Expired - Fee Related US4531602A (en)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
DE19823225053 DE3225053C2 (de) 1982-07-05 1982-07-05 Hydraulische Hilfskraftlenkung für Fahrzeuge mit einem Drosselventil zur Bildung eines Reaktionsdruckes
DE3225053 1982-07-05
DE19823247745 DE3247745C2 (de) 1982-07-05 1982-12-23 Hilfskraftlenkung für Fahrzeuge mit einem Modulierventil zur Bildung eines Reaktionsdruckes
DE3247745 1982-12-23

Publications (1)

Publication Number Publication Date
US4531602A true US4531602A (en) 1985-07-30

Family

ID=25802824

Family Applications (1)

Application Number Title Priority Date Filing Date
US06/510,196 Expired - Fee Related US4531602A (en) 1982-07-05 1983-07-01 Power steering system

Country Status (5)

Country Link
US (1) US4531602A (it)
JP (1) JPH0653497B2 (it)
FR (1) FR2529524B1 (it)
GB (1) GB2131364B (it)
IT (1) IT1168203B (it)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4637484A (en) * 1984-04-20 1987-01-20 Koyo Jidoki Kabushiki Kaisha Hydraulic control apparatus for a power steering device
US4784041A (en) * 1985-08-09 1988-11-15 Zahnradfabrik Friedrichshafen, Ag. Servosteering pressure control device
US4784235A (en) * 1984-10-11 1988-11-15 Koyo Seiko Kabushiki Kaisha Oil pressure reaction control valve for power steering apparatus
US4898074A (en) * 1987-07-02 1990-02-06 Daimler-Benz Ag Servo-valve arrangement for power steering
US5582264A (en) * 1992-07-25 1996-12-10 Zf Friedrichshafen Ag. Power assisted steering system, in particular, for motor vehicles

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0645343B2 (ja) * 1984-04-27 1994-06-15 豊田工機株式会社 動力舵取装置の操舵力制御装置
FR2610274B2 (fr) * 1984-08-09 1989-05-26 Renault Distributeur rotatif perfectionne pour mecanismes de direction assistee
FR2568843B1 (fr) * 1984-08-09 1986-12-26 Renault Distributeur rotatif perfectionne pour mecanisme de direction assistee
JPS61247575A (ja) * 1985-04-25 1986-11-04 Toyoda Mach Works Ltd 動力舵取装置の操舵力制御装置
EP2647966B2 (de) † 2012-04-04 2017-08-23 Siemens Aktiengesellschaft Messwertgeber zum Erhalt einer Positionsinformation und Verfahren zu dessen Betrieb

Citations (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1040392B (de) * 1956-07-18 1958-10-02 Daimler Benz Ag Servolenkvorrichtung fuer Kraftfahrzeuge
US2893504A (en) * 1954-12-30 1959-07-07 Gen Motors Corp Hydraulic steering system with control means for valve reaction pressures
GB1300679A (en) * 1970-06-01 1972-12-20 Nissan Motor A hydraulic power steering device for a vehicle
GB1302323A (it) * 1970-08-06 1973-01-10
DE2356835A1 (de) * 1972-11-15 1974-07-04 Nissan Motor Steuereinrichtung fuer eine servolenkung
GB1392079A (en) * 1971-07-15 1975-04-23 Nissan Motor Hydraulic pressure control valve for use in a power-assisted steering system of a motor vehicle
US3924705A (en) * 1971-12-08 1975-12-09 Aisin Seiki Power steering mechanism
US4119172A (en) * 1976-02-17 1978-10-10 Nissan Motor Company, Ltd. Steering force control system
DE2851773A1 (de) * 1978-11-30 1980-06-04 Zahnradfabrik Friedrichshafen Hydraulische lenkeinrichtung mit rueckwirkung auf die betaetigungseinrichtung
DE2950525A1 (de) * 1979-12-15 1981-06-19 Zahnradfabrik Friedrichshafen Ag, 7990 Friedrichshafen Hilfskraftlenkung fuer kraftfahrzeuge
DE3122370A1 (de) * 1981-06-05 1982-12-23 Zahnradfabrik Friedrichshafen Ag, 7990 Friedrichshafen "servolenkung, insbesondere fuer kraftfahrzeuge"
DE3220922A1 (de) * 1981-06-05 1983-03-17 Zahnradfabrik Friedrichshafen Ag, 7990 Friedrichshafen Servolenkung, insbesondere fuer kraftfahrzeuge

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE295052C (it) *
JPS5297525A (en) * 1976-02-12 1977-08-16 Nissan Motor Co Ltd Device for controlling steering force of power steering apparatus
JPS5299523A (en) * 1976-02-14 1977-08-20 Nissan Motor Co Ltd Device for controlling steering force of power steering system
JPS5642507A (en) * 1979-09-17 1981-04-20 Yanmar Agricult Equip Posture controller of riding type rice transplanter
JPS57140275A (en) * 1981-02-25 1982-08-30 Hino Motors Ltd Power steering
JPS5885572U (ja) * 1981-12-07 1983-06-10 カヤバ工業株式会社 動力舵取装置

Patent Citations (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2893504A (en) * 1954-12-30 1959-07-07 Gen Motors Corp Hydraulic steering system with control means for valve reaction pressures
DE1040392B (de) * 1956-07-18 1958-10-02 Daimler Benz Ag Servolenkvorrichtung fuer Kraftfahrzeuge
GB1300679A (en) * 1970-06-01 1972-12-20 Nissan Motor A hydraulic power steering device for a vehicle
GB1302323A (it) * 1970-08-06 1973-01-10
GB1392079A (en) * 1971-07-15 1975-04-23 Nissan Motor Hydraulic pressure control valve for use in a power-assisted steering system of a motor vehicle
US3924705A (en) * 1971-12-08 1975-12-09 Aisin Seiki Power steering mechanism
US3901343A (en) * 1972-11-15 1975-08-26 Nissan Motor Vehicle power steering control system
DE2356835A1 (de) * 1972-11-15 1974-07-04 Nissan Motor Steuereinrichtung fuer eine servolenkung
US4119172A (en) * 1976-02-17 1978-10-10 Nissan Motor Company, Ltd. Steering force control system
DE2851773A1 (de) * 1978-11-30 1980-06-04 Zahnradfabrik Friedrichshafen Hydraulische lenkeinrichtung mit rueckwirkung auf die betaetigungseinrichtung
DE2950525A1 (de) * 1979-12-15 1981-06-19 Zahnradfabrik Friedrichshafen Ag, 7990 Friedrichshafen Hilfskraftlenkung fuer kraftfahrzeuge
DE3122370A1 (de) * 1981-06-05 1982-12-23 Zahnradfabrik Friedrichshafen Ag, 7990 Friedrichshafen "servolenkung, insbesondere fuer kraftfahrzeuge"
DE3220922A1 (de) * 1981-06-05 1983-03-17 Zahnradfabrik Friedrichshafen Ag, 7990 Friedrichshafen Servolenkung, insbesondere fuer kraftfahrzeuge

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4637484A (en) * 1984-04-20 1987-01-20 Koyo Jidoki Kabushiki Kaisha Hydraulic control apparatus for a power steering device
US4784235A (en) * 1984-10-11 1988-11-15 Koyo Seiko Kabushiki Kaisha Oil pressure reaction control valve for power steering apparatus
US4784041A (en) * 1985-08-09 1988-11-15 Zahnradfabrik Friedrichshafen, Ag. Servosteering pressure control device
US4898074A (en) * 1987-07-02 1990-02-06 Daimler-Benz Ag Servo-valve arrangement for power steering
US5582264A (en) * 1992-07-25 1996-12-10 Zf Friedrichshafen Ag. Power assisted steering system, in particular, for motor vehicles

Also Published As

Publication number Publication date
FR2529524A1 (fr) 1984-01-06
GB8318090D0 (en) 1983-08-03
FR2529524B1 (fr) 1987-01-30
IT1168203B (it) 1987-05-20
GB2131364A (en) 1984-06-20
IT8348527A1 (it) 1984-12-17
GB2131364B (en) 1986-07-30
JPS5920772A (ja) 1984-02-02
IT8348527A0 (it) 1983-06-17
JPH0653497B2 (ja) 1994-07-20

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